Apart from other industries, the aerospatial industry uses large quantities of cables for controls and electric linkings and in particular for supersheathed shielded cables constituted by a plurality of electric conductors insulated by a lateral sheathing. These conductors, placed beside each other in a bundle, are surrounded by a shielding covered with a nonconductive protective sheath.
So as to be able to use and connect these conductors, it is necessary to expose their extremities. This stripping operation mainly consists of removing over a certain length the outer protective sheath of the cable so as to reveal the extremity of the shielding without damaging it.
Currently known stripping devices, whether they be thermic or mechanical, are not satisfactory.
Automatic knife-shaped strippers marrying the geometry of cables are not applicable to cables not having any symmetry of revolution, such as twisted shielded cables, and for which only the manual scalpel is acceptable. However, this scalpel technique is primitive, takes time and rapidly becomes restricting as soon as the cabling volume becomes significant and is random in that it is dependent on the skill of the operator, involves systematic quality control and nevertheless results in a considerable volume of waste.
The risk of cable damage may be reduced by the use of thermic strippers which are particularly effective for fine round conductors.
However, these tools are slow and require an accurate calibration of the heating electrodes whose temperature and cleanliness need to be frequently controlled. Unfortunately, this method is unsuitable for polyimide films not having any melting point. The same applies to certain nonconductors which have a tendency to adhere to the conductor wires after heating.
Moreover, the laser is also used for attacking by means of ablation the outer sheath of a cable, that is by heating and then vaporizing the absorbant material. The absence of any contact between the cutting device and the cable makes it possible, should the operating ranges permit it, to envisage good reproducibility of the stripping operation, the result being completely dissociated from the skill or knowhow of operators.
There are currently a number of machines able to cut the outer nonconductor by means of a laser beam.
This method functions for a single circular cable with a constant thickness. The principle is based on the focussing of the beam by acting on the reflection indices of the existing materials, as well as on the wavelengths they are able to absorb.
The action of the laser beam is limited to the focussing zone whose dimensions are too restricting for taking into account coating profile variations so that, in the case of cables or conductors having no symmetry of revolution, the stripping of the outer sheath is unhomogeneous.
Unfortunately, a large number of cables used in the aeronautical and spatial industries are not cylindrical and have unhomogeneous shapes and particular shieldings and nonconductors.
Thus, there is a need to develop a new stripping principle able to be applied to all types of cables and responding to the essential requirement of full quality. Namely, the clear and clean cutting without damaging subjacent films and able to fully automate cables, except for their placing and removal.